Rotary actuators, such as electric motors, are used in a wide variety of applications. Many modern technologies, such as microsatellites (or “microsats”), unmanned aerial systems, and homeland security surveillance devices, have increased the demand for electric rotary motors of reduced size that still provide high amounts of torque.
Conventional rotary electric motors include a series of electromagnets (e.g., on a stator), including conductive coils wrapped around ferromagnetic “teeth,” arranged in a circular fashion and a series of permanent magnets (e.g., on a rotor), also arranged in a circular fashion, that are coupled to the electromagnets in such a way that they can rotate relative to the electromagnets. Typically, to cause rotation, current is conducted through the coils of a first portion of the electromagnets in a first direction, while current is conducted through the coils of a second portion of the electromagnets in a second direction. In order to continue rotation greater than 360°, the direction in which the current is conducted through the coils is repeatedly reversed or “commutated,” which is sometimes accomplished using alternating current (AC) power. The commutation of the current generally utilizes complicated electronics, especially in high speed applications, which increases the overall size required for the system and the manufacturing costs of the motor.
Additionally, because of the inherent magnetic attraction between the permanent magnets and the teeth, the rotor has a tendency to in particular angular orientations, phenomenon known as “detent torque” or “detent.” The detent torque may cause the electric motor to generate different amounts of torque at different angular positions, which may result in vibrations and impair system performance.
Accordingly, it is desirable to provide a rotary motor that can rotate greater than 360° without requiring current commutation. In addition, it is desirable to provide a rotary motor with reduced size and detent torque that is capable of generating high amounts of usable torque. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.